Scientists say that Mercury has wrinkles because it is declining in size

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Many scientists have assumed Mercury is decreasing over billions of years, but recent evidence reveals it may still be, leaving fractured creases.

In an editorial for The Conversation, planetary scientist David Rothery, a professor at the UK’s Open University and co-author of a Nature Geoscience publication, suggested that Mercury’s crust creases may be caused by ongoing cooling and contraction.

Telescopic data has shown that Mercury’s crust shrank due to interior cooling and formed “scarps” since the 1970s. The creases formed like those on an old apple when the globe squeezed 8.8 miles in diameter during the previous 3.8 billion years, according to Rothery.

Rothery and Open University PhD student Ben Man examined Mercury’s “grabens,” which are small cuts on the backs of the ridge-like scarps that line its surface, to see if it was still shrinking.

Grabens, which are less than 300 feet deep and less than half a mile long, form when the scarps stretch due to “Mercury quakes” and are like toast cracks, as Rothery demonstrated.

This minor fissure, which the researchers believed would have smoothed out if it were as old as the scalps, prompted Man and Rothery to assume Mercury is still shrinking.

Rothery told Insider, “Because there are such small structures, they wouldn’t survive too long.”

Compared to Mercury’s wrinkles, most grabens are less than 300 million years old, according to a British scientist.

After orbiting Mercury, NASA’s MESSENGER spacecraft photographed hundreds of probable grabens and 48 graben-positive scarps between 2011 and 2015. Following that mission, scientists have wondered if Mercury is still shrinking, and NASA stated in 2017 that certain grabens may be as “young” as 50 million years old.

The 2018 European and Japanese BepiColombo probe mission hopes to help scientists understand the phenomenon. The spacecraft has passed Mercury twice and will return in 2026 to acquire higher-resolution photographs than MESSENGER to confirm the 244 “probably” grabens.

That might help scientists better understand the phenomena and determine if the solar system’s smallest planet is still seismically active and shrinking like an old apple.

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